We present a general strategy for generating full atomistic models of
nanopolycrystalline materials including bulk and thin film. In particular,
models for oxidenanoparticles were constructed using simulated amorphisation and
crystallisation and used to populate a library of oxidenanoparticles (amorphous
and crystalline) with different radii. Nanoparticles were then taken from this
library and positioned, within a specific volume, using Monte Carlo techniques,
to facilitate a tight-packed structure. The grain-size distribution of the
polycrystalline material was controlled by selecting particular sized
nanoparticles from the library. The (randomly oriented) grains facilitated a
polycrystalline oxide, which comprised a network of general grain-boundaries. To
help validate the model, gas diffusion through the (polycrystalline) oxide
material was then simulated and the activation energy calculated directly.
Specifically, we explored Hetransport in UO2, which is an important material
with respect to both civilian and military applications. We found that
Hetransport proceeds much faster through the grain-boundary and grain-junction
network compared with intracrystalline UO2 regions, in accordance with
experiment.